The catalysts of this invention have a high activity for the production of unsaturated nitriles at a relatively low reaction temperature. This high activity at a low reaction temperature is surprising in view of U.S. Pat. No. 2,904,580 issued Sept. 15, 1959, which discloses a process for the production of acrylonitrile from propylene and ammonia in the presence of a catalyst selected from the group consisting of bismuth, tin and antimony salts of molybdic and phosphomolybdic acids and bismuth phosphotungstate, and U.S. Pat. No. 3,226,422 issued Dec. 28, 1965, which discloses a catalyst comprising the oxides of iron, bismuth, molybdenum and phosphorus for the production of unsaturated nitriles from olefin-ammonia mixtures.
In addition to high activity for nitrile production, the catalyst employed in the process of this invention has a number of other important advantages that contribute greatly to the efficient and economic operation of the process. The catalyst has excellent redox stability under the reaction conditions of the process. This permits the use of low process air to olefin ratios and high weight hourly space velocities. The catalyst exhibits efficient ammonia utilization thus greatly reducing the amount of unreacted ammonia appearing in the reactor effluent and thus lowering the amount of sulfuric acid required to neutralize the ammonia in the effluent. Improvements are obtained in the recovery section operation and pollution control resulting from the lowering of polymer waste products that are formed. The catalyst performs optimally at a lower reactor temperature than is normally employed for this type of reaction with per pass conversions to the nitrile product as high as 80 percent and above. Use of lower operating temperatures favors longer catalyst life and minimizes effluent problems such as afterburning. Ease of catalyst preparation and lower cost of the essential catalytic components are additional benefits that can be realized with the use of the catalyst of this invention.